Stabilization of dichlorobutadiene resins



Patented July 20, 1948 STABILIZATION F DICHLOROBUTADIEN E RESINS George P. Rowland, Jr., Pottstown, Pa., and Robert J. Reid, Canal Fulton, Ohio, assignors to The Firestone Tire & Rubber Company, Akron, Ohio, a corporation of Ohio No Drawing. Application August 10, 1947, Serial No.'769,0'l6

14 Claims.

This invention relates to the stabilization, against deterioration by light and oxidation, of resinous polymers and copolymers of 2,3-dichlorobutadiene-l,3, hereinafter referred to, for brevity as dichlorobutadiene. In general, the invention is based upon the discovery that the resistance to light and oxidation of such polymers and copolymers may be greatly enhanced by the addition thereto of mercaptols and mercaptals.

THE DICHLOROBUTADIENE RESIN Referring first to the dlchlorobutadienc polymers which may be stabilized in accordance with this invention, this material has been polymerized heretofore to yield products aptly described as hard, infusible and insoluble. While such refractory resins may be stabilized in accordance with this invention, it has recently been discovered that, providing certain precautions are observed, dichlorobutadiene may be polymerized to yield resins which are fusible to fluid melts, are soluble in hot solvents, and have crystalline properties similar to those of the nylon and vinylidene chloride resins-i. e., they may be extruded, and cold stretched to yield filaments, cordage, etc. having excellent strength and flexibility and exhibiting oriented-crystalline X-ray patterns. These latter resins are clearly of great technical merit, and accordingly, the invention is more particularly directed to the stabilization of such crystalline resins. However, it is to be understood that any of the polymers and copolymers of dichlorobutadiene containing a sufllcient amount of dichlorobutadiene (say from about. to 100%, based on the total weight of resin) so that the failure thereof under exposure to light and oxidation occurs via mechanisms dependent on the polydichlorobutadiene structure, may be stabilized in accordance with this invention,

More particularly with respect to the crystalline dichlorobutadiene resins above alluded to, it is thought, without absolute commitment to this theory, that the casually produced polymers of dichlorobutadiene described in the prior art were intensively cross-linked, degraded, etc., and were therefore incapable of asserting any tendency which the dichlorobutadiene polymer chain may have toward crystalline behavior. At any rate, it has recently been found that, providing certain precautions are observed in the production of dichlorobutadiene polymers and copolymers, there are obtained crystalline resins comparable to nylon and vinylidene chloride resins. These precautions are:

2 1. A restrained chlorination of a refractory dichlorobutadiene polymer of the prior art, the chlorine uptake being strictly confined to the range 2.-10%, and preferably 3-5%-, based on theweight of polymer, This degree of chlorination does not appear to alter the essential polymeric chain, but merely breaks up crosslinks, side structures, hyper-polymerized nuclei, etc.

2. The use of modifying agents, as the term is understood in the synthetic rubber art, to include certain polymerization-controlling anddirecting substances such as lauryl mercaptan, butyl mercaptan, thiophenols, hexamethylene dimercaptan, diisopropyl xanthogen disulfide, etc. The inclusion, in the polymerization mixture, of from 0.5% to about 3% of these materials, based on the weight of monomers (including comonomers as detailed below) will develop highly crystalline properties in the resultant resins. The technique is applicable to solution, emulsion, or mass polymerization.

3. Polymerization in non-reacting organic solvents, e. g., toluene. benzene, methanol, ethanol, ether, hexane, etc., in concentrations of from-about 10% to about based on the total weight of solvent and of dichlorobutadiene, at relatively elevated temperatures on the order of from about 0 C. to about C., and in the presence of from about 0.1% to about 5.0%, based on the total weight of polymerization mass, of a peroxidic catalyst such as benzoyl peroxide.

Of all these techniques, that outlined under (2) is the most practical for the manufacture of resins for extrusion and orientation into filaments, to the stabilization of which the present invention is of especial application.

Asnoted above, the present invention may be applied to the stabilization both of homopolymers of dichlorobutadiene and of copolymers thereof with unsaturated compounds copolymerizable therewith. Dichlorobutadiene is readily copolymerizable with a wide variety of unsaturated compounds which are themselves addition-polymerizable; and the stability of the resultant resins is materially enhanced by the addition of mercaptols in accordance with this invention, provided that the dichlorobutadiene is present to an extent (say 25% to 100%, based on the weight of resin) such that the mechanism of degradation thereof contributes substantially to the ultimate failure of the resin. it is understood that, if the resin is to be of the fusible, crystalline type, it must not contain more than about 2% of a cross-linking comonomer (i. e., a plurally unsaturated comonomer in which theethylenic groups are not conjugated or cross-conju ated) nor more than about -15% of any other comonomer. These last two restrictions do not apply, if fusible crystalline resins are not desired. Suitable non-crosslinking comonomers are exemplified'in vinyl compounds on the order of vinyl ethyl ether, vinyl pchloroethyl ether, vinyl higher fatty ethers, vinyl phenyl ether, etc.; vinyl ketones such as vinyl methyl ketone, methyl isopropenyl ketone, vinyl phenyl ketone, etc.; cyclic vinyl compounds such as styrene, a-methyl styrene, nuclearly chlorinated styrenes, p-vinyl benzoic acid, p-vinyl naphthalene, vinyl benzoate, vinyl carbazole, various vinyl pyridines, and the like; acrylic and substituted acrylic compounds such as methyl acrylate, methyl methacrylate, vinyl furane, ethyl chloroacrylate, methacrylonitrlle, chloroacrylonitrile, acrylonitrile and the like; vinylidene halides such as vinylidene chloride, vinylidene bromide, l-fluoro-l-chloro-ethylene; 1,1-dichloro-2,2-difluoro-ethylene; compounds bearing an active cyclic unsaturated carbon atom such as coumarone, indene, 4- methylene-l,3-dioxolane, substituted derivatives of this material, and the like. Examples of suitable conjugated and cross-conusing the notation of Formula I above.

The reaction may be carried out combining the aidehyde or ketone and the mercaptans, with application, if necessary, of heat on the order of 0 C.-

, 150 C, and with addition of catalysts such as HCl', ZnClz, p-toluene sulfonicacid, etc; Aldehydes and ketones suitable for this reaction will be seen to include, for example, acetone, formaldehyde, acetaldehyde, mesityl oxide, acetonyl acetone, benzaldehyde, glyoxal, dibenzal acetone, chloral, cinnamaldehyde, cinnamal acetone, 2,3- dlmethoxybenzaldehyde, acrolein, 2-ethyl-3-prov pyl acrolein, is'ophorone, camphor, acetyl acetone jugated copolymerizable compounds are butadiene, cyclopentadiene, chloroprene, l-chlorobutadiene, isoprene, 2,3-dimethyl butadiene-1,3, piperlyene, 2-methyl pentadiene, etc.

THE MERCAPTOLS AND MERCAPTALS' The mercaptols and mercaptals which may be employed in accordance with this invention may be any organic compounds having the formula wherein R1 and R2, each independently of the other, indicates a hydrogen atom or an organic radical, a carbon atom of which is directly attached to the central carbon atom C' of the formula, which organic radical may be simple aliphatic, araliphatic or aromatic hydrocar: bon, or may contain non-hydrocarbon groupings and substituents not inimical to the stability of the dichlorobutadiene resin, such as ether, thioether, ester; thioester, ketone, alde- These mercaptols, as implied in their names, may conveniently be produced by the condensation of an aldehyde or ketone with one or more mercaptans in accordance with the reaction and the like. Suitable mercaptans will be seen to include, for example, cetyl mercaptan, dodecyl mercaptan, n-octyl mercaptan, butyl mercaptan,

VZ-ethyl hexyl mercaptan, thiophenol. thio-p-cresol, thio-p-naphthol, tetramethylene dimer-captan, mercaptobenzothiazole, u-pinene mercaptan, thioglycolic acid, the addition products of hydrogen sulfide to diisobutylene and to triisobutylene and the like. Specific suitable resultant mercaptols and mercaptals are exemplified in acetone dicetyl mercaptol; mesityl oxide -di-noctyl mercaptol; acetonyl acetone tetracetyl mercaptol; benzal thio-p-cresol mercaptol; benzaldehyde-di-thlo-fl-naphthol mercaptol; chloral didodecyl mercaptol; dicinnamal acetone dicetyl mercaptol; dibenzal acetone di(thio-p-naphthol) mercaptol; 2,3-dimethoxy benzaldehyde di(thiop-naphthol) mercaptol; benzal thio-p-cresoi mercaptol; glyoxal tetraacetyl mercaptol; lauraldehyde thio-p-naphthol mercaptol; acetone dicetyl mercaptol; 2-ethyl-3-propyl acrolein cetyl mercaptol; acetone dibutyl mercaptol; acetyl acetone tetraacetyl mercaptol; acetyl acetone tetraoctyl mercaptol; acetone di-t-decyl mercaptol; acetyl acetone di-t-butyl mercaptol; didodecyl mercaptol of camphor and the like.

AMOUNT AND COMIPOUNDING OF IWERCAPTOLB The addition, tea polymer or copolymer of vdichlorobutadiene, of as little as 0.5%, based on the weight of resin, of a suitable mercaptol, will definitely enhance the resistance thereof to light and oxidative deterioration. Increasing quantities, up to about 2%, will give still further enhanced stability, rendering the polymers and copolymers suitable for the most rigorous conditions of service. Still greater quantities, on the order of 3% to 6%, may be used, but will ordinarily be found wasteful. I

' While the stabilizers of this invention may be used alone, and when so used provide excellent protection of dichlorobutadiene resins against delifrioration by light, particularly excellent resu s are obtained when the stabilizers of this invention are employed in conjunction with a combination of (A) a light screening agent and preferably, but not necessarily, (B) a mild antlacid. The resins so protected have stabilities not attainable by the use of any of the individual components alone. Light-screening agents are a wellknown class of materials which are compatible with resins and which bar the transmission of actinic rays, and include for instance phenyl salicylate; o-cresoxy-ethyl o benzoylbenzoate: p-benzoyl phenylsalicylate; bisphenol A disalicylate; t-butyl catecholyl disalicylate: triphenyl fcarbinol; 2-6-t-butyl-4-methyl phenyi salicylate; p-tert-butyl-phenyl sallcylate; 2,2'-dihydroxy benzophenone; p-nonyl phenyl salicylate, p-ethyl phenyl salicylate, p-octyl phenyl salicylate, salicylic acid reaction products of alkyl- 6 ated cresylic acids, and the like. In general, 3 salicylic esters oi alkyiated phenols are the preferred compounds for this'purpose. Most oi. the Mercgptol stabilizer (per above listed compounds also act as plasticizers. Table I) .01, .02 or .03 Suitable ant'iacids include alkyl tin compounds 5 grams (per m I) such as di-butyl tin diacetate. dibutyl tin di- Ac ton ,g t dissolve salicylate, tributyl tin acetate, tetraphenyl tin, epoxy compounds such as styrene oxide" epoxy A series or stabilized compositions were made compounds of oieic acid esters, naphthyl ethylene "P 0011131166 h the B E ip using oxide. and the m each of the mercaptols in each of the proportions mcmombutadiene polymers and copolymers listed in Table I. In each case, the selected merstabilized in accordance with this invention are cflplol'was dissolved in a quantity of on sumcharacterized by a high degree of re ista e t clent toefl'ect the solution thereof, yielding a solight and oxidative deterioration, rendering them luuon be designated 2 The dicmombuta" highly suitable for any ordinary commercial apresin and acetone listed at were Slurried plications. Particularly when dichlorobutadiene together, solution added thereond the resins are worked up into forms presenting a large entire suspension dried with stirring to Yield a ratio of surface area to volume, as in oriented- Powder having the selected mercaptol Evenly crystalline filaments, foils, etc., and still more dispersed theremparticularly where these oriented products are A gram Sample of the dried Powdered resin destined f applications subject to exposure, as was then inserted between Cellophane sheets and in outdoor furniture upholstery, transportation the assembly Pressed between flat platens main upholstery, packaging films and t like the 6D,, tained at 180 C. under a total load Of 2500 hanced lightand oxidation-resistance imparted pounds- The assembly was c018d in e D s by the practice of this invention is of distinct adand then removed, yieldlns a thin n parent vantaga plaque usually approximately 3000 sq. mm. in

With the foregoing general discussion in mind, there are given herewith detailed examples of the strips cut from this Plaque were then exposed practice of this invention. All parts given are by under the set in the T. M. weight, t t D-62 -45T, using a General Electric Company S-l sunlamp bulb as the light source. Sam- PREPARATION OI DICHLOROBUTADIE" R151" ples were removed after exposure of 1, 2, 3 and 20 P t hours, and rated as to color on a subjective scale Dichlorobutadiene 100 in which a ye ow brown was assigned the num- Water (distilled) 400 her 10. and colors evenly grading up from t t Potassium persulfate 1.0 Of the unexposed resin to that of the yellow brown Disodium p osphate were assigned the numbers 0, 1, 2, 3 9, The Sodium salt of diamyl sulfosuccinate .27 ratings given the various exposed samples after Amyl mercaptfln various times 01' exposure are set out in Table 1 The above ingredients were agitated in a sealed in the columns under C0 0 autoclave at a temperature 0! 27 C. for 18 hours. wl those a ple removed at the end of The water was preliminarily deaerated by boiling, 20 hours were examined and were variously rated followed by cooling while bubbling nitrogen as "brittle" if they cracked upon repeated flexure; therethrou h. and a atmosphere of nitrogen w 5 or "cracked" if they merely developed surface hair maintained in the autoclave throughout the relines uponflexum These ratings, together with actioh- The resultant latex was emulated by supplementary observations are likewise included addition of methanol, and the precipitate was m Table L under the heading Physical prop separated by filtration and tholrouglhly lwiashed an the'filter with additionalmet ano e resu ant granular resin was thermoplastic and extrudi if z' ig f gfi gigg g 1; f item able, and exhibited crystalline properties simik y e seen a a very to nylon and vinyndene chloride resms This mar ed increase in resistance to discoloration is resin was used as the standard base resin for the with the remammg items mmammg stabilization tests to 0110 mercaptols in accordance with this invention.

Likewise, it will be noted that the region of di- 1 minishing returns is attained by the addition oi A more than 2% of mercaptol, note that the items containing 3% of mercaptoi exhibit little if any is f ffffi i f i fififi ii 1 gram improved stability over comparable items con- Acetone .5 ml. taming only 2% of mercaptol.

Table I Dlsooloratlon Alter- Stabilizer 3 m, i ii i k g h 1hr. 2hr. 3hr. 2011:.

Blank (ll g very brittle. Acetone Dieetyl Mercaptol g i g 2 slightly brittle.

i s 4 t 10 B X Mesityl Oxide-di-n-octyl mercaptol 3 g g tt e.

ll 12 Table II-C'ontinued I Color After- Physical Mercaptol (a1) Light-screening agent Antiacid Fromm 21in. 3lirs. 201m. Remarks Dibenzalacetone.. 0 2 Cr. Dibutyltln dlsallcylate 'lributyltin acetate 0 0 4 B Triplienyl carblnoL. 0 0 4 Z-G-dl-t-hutyl-Q-methyl phenal 0 0 3 qiiififfiiflfiili'ii'fffiiiii 3 .3 Z 'lriphenyl carbinol 0 0 2 Cr. i-Bfliylwmwvisalicvlm Bitfii'fifittiirenaaa:3111111311131: 3 8 3 Exam m A ll 2. An oriented crystalline filament comprising Parts a homopolymer of 2,3-dichlorobutadiene-l,3, to- Base dichlorobutadiene resin J00 gether with at least 0.5% of a compound selected Acetone dicetyl mercaptol 1 from the group consisting of mercaptols and Dibenzal actone 1 mercaptals having the formula Dibutyi tin diacetate 1 :0 Dioctyl phthalate RP The foregoing recipe was selected, from amongst the combination set out in Table II, as giving excellent all-around performance. The

listed ingredients were ball-milled together to yield an even dispersalof all components, and then extruded at 185 C. through a .02" die into a water quenching bath maintained at 15 C. The quenched filament was then immediately stretched to 400% of its original length by means of differential rollers, yielding an oriented-crystalline monofilament having a diameter of .008"

and a tensile strength of 38,000 pounds per in).

The resultant monofllament was woven into a square weave upholstery fabric whichgave excellent performance as a convertible coup automobile seat cushion covering, under severe conditions of exposure to sunlight and weather.

In view of the foregoing general discussion and detailed specific examples, 'it will be seenthat this invention provides a novel and highly effective means for the stabilization of dichlorobutadiene resins against deterioration .by light and oxygen. This efiective protection is of particular advantage in oriented crystalline monofllaments and films made from such resins, since the conditions of exposure thereof are quite severe. The stabilizers may be synthesized from readily available aldehydes, ketones and mercaptans.

What is claimed is:

1. A resinous composition resistant to deterioration by light and oxidation, comprising a resin selected from the group consisting of homopolymers of 2,3-dichlorobutadiene-1,3 and copolymers thereof with not more than 75%, based on the weight of such copolymers, of other unsaturated compounds copolymerizable therewith, together with at least 0.5%, based on the weight of resin, of a compound selected from the group consisting of mercaptols and mercaptals having the formula wherein R1 and R2, each independently of the other, represents a hydrogen atom or an allphatic, araliphatic or aromatic radical attached wherein R1 and R2, each independently of the other, represents a hydrogen atom or an all phatic, araliphatic or aromatic radical attached through one of its carbon atoms to. the central carbon atom C of the formula, and R3 and R4, each independently of the other, represents an aliphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the adjacent sulfur atom of the formula.

3. A resinous composition resistant to deterioration by light and oxidation, comprising a resin selected from the group consisting of polymers of 2,3-dichlorobutadiene-1,3 and copolymers thereof with not more than based on the weight of such copolymers, of other unsaturated com-pounds copolymerizable therewith, together with (A) atleast 0.5%, based on the weight of resin, of a compound selected from the group consisting of mercaptols and mercaptals having the formula S-Ri R1C'R:

wherein R1 and R2, each independently of the other, represents a hydrogen atom or an allphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the central carbon atom C' of the formula, R3 and R4, each independently of the other, represents an allphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the adjacent sulfur atom of the formula; (B) a light-screening agent and (Q) an antiacld.

4. A resinous composition resistant to deterioration by light and oxidation, comprising a resin selected from the group consisting of polymers of 2,3-dichlorobutadiene-1,3 and copolymers thereof with not more than 75%, based on the weight of such copolymers, of other unsaturated compounds copolymerizable therewith, together with (A) at least 0.5%, based on the weight of resin, of a compound selected from the group consisting of mercaptols and mercaptals having the formula wherein R1 and R2, each independently of the other, represents a hydrogen atom or an all- 13 phatic, araliphatic or aromatic radical attached through one of its carbon atomsto the central carbon atom C of the formula, and R: and R4, each independently of the other, represents an aliphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the adjacent sulfur atom of the formula; and (B) a salicylic ester of an alkylated phenol.

5. An oriented-crystalline filament comprising a resinous polymer of 2,3-dichlorobutadiene-l,3, together with, based on the weight of polymer, at least 0.5% of acetone dicetyl mercaptol.

6. An oriented-crystalline filament comprising a resinous polymer of 2,3-dichlorobutadiene-1,3, together with, based on the weight of polymer, at least 0.5% of acetyl acetone dicetyl mercaptol.

7. An oriented-crystalline filament comprising a resinous polymer of 2,3-dichlorobutadiene-l,3, together with at least 0.5% of each of the com' pounds acetyl acetone dicetyl mercaptol, paratertiary-butyl catechol salicylate and tributyl tin acetate.

8. Process of stabilizing a resin selected from the group consisting of polymers of 2,3-dichlorobutadiene-l,3 and copolymers thereof with not more than 75%, based on the weight of copolymer, of other unsaturated compounds copolymerizable therewith, which comprises adding to the selected resin at least 0.5%, based on the weight of resin, of a compound selected from the group consisting of mercaptols and mercaptals having the formula atom of the formula.

9. Process of stabilizing a resinous polymer of 2,3-dichlorobutadiene-1,3, which comprises adding thereto at least 0.5%, based on the weight of resin, of a compound selected from the group consisting 'of mercaptols and mercaptals having the formula S-Bg nr-d -a,

wherein R1 and R2, each independently of the other, represents a hydrogen atom or an aliphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the central carbon atom C of the formula, and R: and R4, each independently of the other, represents an aliphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the adjacent sulfur atom of the formula.

14 10. Process of stabilizing a resin selected from the group consisting of polymers of 2,3-dichlorobutadiene-1,3 and copolymers thereof with not more than 75%, based on the weight of copolymer, of other unsaturated compounds copolymerizable therewith, which comprises adding to the one of its carbon atoms to the central carbon atom C' of the formula, and R3 and Bi, each independently of the other, represents an aliphatic, a'raliphatic or aromatic radical attached through one of its carbon atoms-to the adjacent sulfur atom of the formula, (B) a light-screening agent and (C) an antiacid.

11. Process of stabilizing a resin selected from the group consisting of polymers of 2,3-dichlorobutadiene-1,3 and copolymers thereof with not more than 75%; based on the weight of copolymer, of other unsaturated compounds copolymerizable therewith, which comprises adding to the selected resin at least 0.5%, based on the weight of resin, of each of (A) a compound selected from the group of mercaptols and mercaptais having the formula wherein R1 and R2, each independently of the other, represents a hydrogen atom or an aliphatic, araliphatic or aromatic radical attached through one of its carbon atoms to the central carbon atom C of the formula, and R1 and R4, each independently of the other, represents an aliphatic, I araliphatic or aromatic radical attached through one of its carbon atoms to the adjacent sulfur atom of the formula, and (B) a salicyclic ester of an allwlated phenol.

12. Process of stabilizing a resinous polymer of 2,3-dichlorobutadiene-L3, which comprises adding thereto at least 0.5% acetone dicetyl mercaptol.

13. Process of stabilizing a resinous polymer of 2,3-dichlorobutadiene-1,3 which comprises adding thereto at least 0.5% acetyl acetone tetracetyl mercaptol.

14. Process of stabilizing a resinous polymer of 2,3-dichlorobutadiene-1,3 which comprises adding thereto at least 0.5% of each of the compounds (A) acetyl acetone tetracetyl mercaptol, (B) .para-teriary buty-l catechol salicylate and (C) tributyl tin acetate.

Certificate of Correction Patent No. 2,445,739. July 20, 1948.

GEORGE P. ROWLAND, JR., ET AL.

It is hereby certified that errors appear in the printed specification of the above numbered patent requiring correction as follows:

Column 6, line 16, for the word thereon read thereto; column 7, Table 1, 8th

item under the heading Stabilizer, for Chloral di-dodecyl mercaptol read Chloml di-dodecyl mercaptal;

and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Oflice.

Signed and sealed this 7th day of December, A. D. 1948.

THOMAS F. MURPHY,

Assistant Oommz'ssz'oner of Patents. 

